Developers who want to create addictive social games with a broad appeal will need to master game loops, or that chain of actions that players perform over and over -- in FishVille, for example, the game loop is "buy fish, grow fish, sell fish, repeat."

That's actually true for many kinds of games, but for social titles, Henric Suuronen says there are several guidelines that developers need to keep in mind when building the "primary grind" they're putting the players through.

One common mistake that developers make with their studio loop is failing to reward players with in-game money as they go through the core game loop. Suuronen notes that people can't help but want currency as a reward.

"They want to get money [whether] it's imaginary money or real money," he explained during a presentation at GDC Europe last year. The ex-Wooga studio head, now founder of Non Stop Games, warns that if core game loops fail to reward players with in-game cash at the end of a cycle, "the user starts to focus on something else where he gets the soft currency."

It's best to design as few steps as possible in game loops -- four to six steps max, Suuronen advised -- but that doesn't mean developers should make games without complexity. They should implement "smart depth" in those steps, an extra layer of strategy on top of the game loop.

Some examples of smart depth include item interdependency, which rewards players for smart placement of items that have a positive effect on each other; or flow planning that encourages player to plan how optimal paths when laying out their virtual creations.

For those wondering if their already launched social games have social depth, Suuronen said, "If you don't have any YouTube videos with people showing a good optimal layout of their city or restaurant, then you don't have smart depth. The best example of having smart depth is people starting to share a picture of 'Hey, take a look at how smart I was.'"

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